1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, printer, facsimile machine, or the like, and in particular relates to an image forming apparatus using a developer and capable of optimally controlling toner concentration of the developer.
2. Description of the Related Art
In image forming apparatuses such as printers, copiers, or facsimile machines, a developing device as disclosed in JP-2008-299315-A is known.
Recently, for the purpose of saving energy, the apparatus is frequently turned off in a relatively short time after the image formation has been completed. In addition, developer should not be performed after the completion of image formation in order to prevent degradation of the developer inside a developing device. Therefore, the drive of the developing device is frequently stopped immediately after image formation. In such a case, however, if the time until the drive of the developing device is stopped is too short, there may be a case in which all toner replenishment operation by a toner replenishing device is not completed while the developing device is still being driven, thereby causing toner concentration fluctuation to occur. To prevent such a toner concentration fluctuation, it is preferred that the unreplenished portion of the toner replenishment amount excluding the already replenished amount be replenished at a time when the drive of the developing device is resumed.
When the power to the image forming apparatus is turned off until the drive of the developing device is resumed after it has been stopped, there is a disadvantage in that the information relating to the unreplenished portion of the toner replenishment amount is lost when the above information is not stored in a nonvolatile memory or the like. If the above information is lost, the unreplenished toner is not replenished after the drive of the developing device has been resumed, and the necessary amount of toner is not supplied to the developing device, thereby causing the toner concentration of the developer inside the developing device to be decreased.